Two Chinese nationals were among 19 people killed in northern Myanmar on Saturday when ethnic rebels attacked security force posts and a casino in an area bordering China, the foreign ministry said.
Several rockets and stray bullets fell on Chinese territory, it added, and more than 300 refugees have fled to China after the deadliest flare-up in the area in recent years.
"China is highly concerned about the armed conflicts that took place in northern Myanmar on May 12," ministry spokesperson Lu Kang told a regular press briefing Monday.
"According to what we have learned, as of now, the conflict has caused the death of two Chinese nationals in Myanmar, and three rockets and some stray bullets have fallen into Chinese territory."
China has also offered temporary shelter to "more than 300 Myanmar border residents who entered China to flee the violence", Lu said, giving no details of how the Chinese were killed.
The Ta'ang National Liberation Army, one of several insurgent groups fighting for more autonomy in the north, said it launched the operation on Saturday.
"China demands that the parties to the conflict stop the fire immediately, take all measures to prevent further escalation of the situation... and prevent incidents that sabotage the peace and stability in the China-Myanmar border region," Lu said.
Saturday's attack was launched outside the town of Muse in Shan state, which is situated at a crossing and major trading post between Myanmar and China's Yunnan province.
Clashes in the border region in early 2017 sent more than 20,000 Myanmar refugees scrambling across the border into Yunnan, raising tensions between the neighbours.
Rights activists say clashes in northern Myanmar have intensified since January as the international community focuses on the unfolding Rohingya crisis in the west of the country, where the Myanmar army stands accused of an ethnic cleansing campaign.